1. Field of the Invention
The invention relates to a rod flame glow plug for preheating the intake air of an internal combustion engine with autoignition having a housing, which has a fuel connection with metering device and an electric connection, and at least one heating rod, which is placed in the housing and is formed from a glow tube in which at least one regulating coil and at least one heating coil are embedded in a filling material and are connected in series to one another and the electric connection.
2. Description of Related Art
Such a rod flame glow plug, which is known, for example, from German Patent 40 07 340, is used to heat the intake air of an internal combustion engine with autoignition, for example, of a diesel engine, if starting problems in the autoignition occur because of low temperatures.
Rod flame glow plugs are known in configurations with one or more heating rods as well as with single or multiple coil combinations of regulating and heating coils. If a voltage is applied to such a rod flame glow plug, a current flows through the coil combination of regulating and heating coils, so that the heating coil, whose resistance value is almost independent of the temperature, glows first. By heating the regulating coil material, which has a positive resistance temperature coefficient and therefore, with increasing temperature, reduces the current by its inherent resistance, the heating coil is protected from overheating.
The regulating coils usually consist of pure nickel, i.e., Ni 99.9. But this material has a regulating behavior, i.e., a resistance behavior relative to the down-regulation of the current by the temperature, which results in relatively long heating-up times. The flat rise of the temperature curve, which is responsible for the long heating-up time to reach ignition temperature, without timing function when the generator voltage is applied, does not correspond to the requirements for a quick starting of the internal combustion engine, especially within about 15 seconds.